This research proposal suggests experiments to test the hypothesis that changes in the nutritional adequacy of an aminal's diet to such an extent that it will result in a deficiency of one of many key nutrients (e.g., essential amino acids, Thiamine, zinc, oxygen) that results in a food intake depression as a result of a "receptor", responding to metabolite levels in the central nervous system and possibly elsewhere. The experiments described in this proposal suggest experiments which involve lesioning certain areas of the brain, implanting electrodes into certain areas of the brain, implanting cannula into certain arteries, veins, or into certain areas of the brain, examining the dietary choice of an animal for or against a nutritionally complete or deficient diet, and determing blood plasma and tissue concentration of key metabolites for each individual study in an attempt to correlate plasma or tissue metabolite levels with the quantity of food eaten, and the dietary selection of the specific diets. Areas of the brain that will be looked at initially are: hypothalamus, prepyriform cortex, and amygdala. Ultimately the work in this proposal should lead to the description of the mechanism of the general and specific effects of nutritional status on food intake regulation and perhaps lead to the knowledge of how a receptor for food intake regulation actively works.